The present invention relates to a method of producing wire harness and, more particularly, to an improvement in the structure of a wiring block which joins in retaining, laying and cutting wires as well as other operations on wires in connection with such a method. The improvement is directed to avoiding fusion of a bridge conventionally relied on to rigidly retain wire ends at predetermined intervals on the bridge and, instead, permitting it to be attached removably on wire ends; the attachment of such a bridge may be performed before laying wires or during any one of successive steps from the laying of wires to the press attaching of metal terminal members onto the wire ends.
We have proposed in U.S. patent application Ser. No. 080,682 filed Oct. 1, 1979. A method and apparatus for the production of wire harnesses in which a wire is laid out and cut off at the same time and, during such an operation, its end is arranged at a suitable spacing from that of an adjacent wire or wires by a bridge. This proposal facilitates quite easy operations which will follow the wire laying and cutting operation, i.e. press attaching terminal members onto wire ends and mounting the terminal members to electric connectors.
According to the patent application mentioned above, wiring blocks are placed in preselected positions on a workbench. These blocks correspond to an intended design or pattern of a product (wire harness). A jig for laying or stretching wires is mounted elevatably on a wiring head which is driven for reciprocation along X and Y axes on the workbench. Each wiring block and the wiring jig cooperates with a wire clamp adapted to clamp and cut wires. By this cooperative mechanism wires are laid between desired wiring blocks and cut off at the same time. Thus, the technical concept of such a proposal is entirely different from that of a traditional system in which a wire is cut to a predetermined length at a first station and then each cut wire is conveyed to a second station with its opposite ends taken hold of.
After the laying of wires on wiring blocks, the workbench is bodily transferred to a fusing station where the bridge on each wiring block will be melted to firmly hold the wires thereon. Then the resultant wire harness is removed from the wiring blocks and brought to a further station where the wire ends will be peeled and terminal members will be pressed onto the peeled wire ends.
The conventional method and apparatus will be described in detail with reference to FIGS. 1-8.
Referring to FIG. 1, the apparatus includes a pair of threaded X shafts Bx extending along opposite longitudinal edges of the workbench D. Cross-beam S is movable on and along X shafts Bx and carries thereon threaded Y shaft By on which wiring head B is movably supported. X shafts Bx are driven for rotation by a first motor (not shown) whereas Y shaft By is driven by a second motor (not shown). By suitably setting the amounts of rotation of shafts Bx and By, wiring head B and wires W held by the head B can be brought to any desired position among the respective blocks A arranged on workbench D. A control unit N is adapted to store an entire process for wiring programmed on a magnetic tape (NC control). Reference number T is a reel station where wires W whose insulative coverings have different colors are stored on independent reels. Wires W are payed out to wiring head B through corresponding capstans U which serve to reduce the magnitude of tension imparted to the wires being driven by a motor (not shown) in the intended direction of wire feed.
When the wire laying and cutting operations are finished, the workbench D slides along a rail R to a next station such that the wires engaged on the wiring blocks A are subjected to a subsequent operation.
Referring to FIG. 2, there is shown a wiring block in a perspective view and generally denoted by the reference character A. The wiring block A has a series of nozzle guide pins 1 at its front upper end and a series of nozzle guide grooves 5 at its rear end. Intermediate between the pins 1 and grooves 5, the wiring block A is provided with a transverse recess 2 for receiving a bridge, pawls 3 for clamping wires and a surface 4 against which the cutting edge of a cutter will abut as will be described. A winged screw 6 is threaded into the wiring block A to open or loosen the clamping pawls 3 when required.
FIG. 3 shows in partly sectional side elevation the wiring head B which runs along X and Y axes on the workbench.
As depicted in side elevation in FIG. 3, wiring head B includes a frame or a head body 7, a plurality of wiring jigs 8 located on top of frame 7 and clamping jig 10 positioned below the frame 7. The jigs 8 and 10 reciprocate and rotate relative to a predetermined position.
Annular member or wiring jig mount B1 for mounting wiring jigs 8 is mounted to frame 7 rotatably through a plurality of guide rollers B2. Jig mount B1 is operatively connected to a limited speed motor B3 circulate in a horizontal plane.
Wiring jigs 8 are passed through respective tubular guides B4 which are spaced equidistant along the circumference of jig mount B1. Each of the wiring jigs 8 is locked at a preselected level by a knock pin B5.
Differently colored wires W are payed out from the reel station T to individual wiring jigs 8. Jig mount B1 when driven by motor B3 will bring a selected wiring jig 8 to a predetermined position P in FIG. 4.
Each jig 8 reaching the position P is reciprocated vertically in accordance with the action of unit B6. Denoted B7 is a motor adapted to drive capstan B8 provided on the jig 8.
As shown in detail in FIG. 5, the clamping jig 10 has a front end clamping plate 11, a wire end guide plate 12, a cutter 14 and a rear end clamping plate 15 which are arranged in succession from the front end to the rear end of the jig. The guide plate 12 is backed up by a coiled compression spring 13. The guide plate 12 and cutter 14 extend downward somewhat beyond the lower ends of the front and rear end clamping plate 11 and 15 and in parallel vertical planes which are perpendicular to those of the latter. The clamping plates 11 and 15 are positioned on the jig 10 symmetrically to each other with respect to the cutter 14.
A bridge C which will be received in the recess 2 of the wiring block A is shown in detailed perspective in FIG. 6. The bridge C serves to hold wire ends at predetermined intervals rigidly therewith. The bridge C is shown to comprise a base 16 in the form of a narrow elongate strip and a series of paired upright pieces 17, 17' which are spaced a predetermined distance from each adjacent pair. In use, the bridge C will be cut into a certain length which corresponds to the selected number of wires to be carried on the bridge. The bridge C is usually made of a thermoplastic resin of the same kind as that of the insulator on a wire W. After wires are laid on the bridge C, the upright pieces 17, 17' on the bridge will be fused to rigidly retain the wires therewith.
The wiring block A, wiring jig 8 and clamping jig 10 will work in cooperation to lay, clamp and cut a wire as will be described hereinafter with reference to FIGS. 7a-7c.
At the start of a wiring operation, a bridge C is placed in the transverse recess 2 of a wiring block A-1 and the nozzle 9 is held in engagement with the bridge C and adjacent nozzle guide pins 1 while being bent in the manner indicated in FIG. 7a. A predetermined length l of wire W emerging from the end of the nozzle 9 is positioned in an upper portion of the clearance space between coactive clamping pawls 3.
As the clamping jig 10 is lowered to a position shown in FIG. 7b, the wire end guide plate 12 on the jig 10 is brought into contact with the wire W to guide it to a point midway between the opposite clamping pawls 3. Then the front end clamping plate 11 presses the wire W until the latter becomes nipped between the clamping pawls 3. At the same time, the wire W is laid between adjacent upright pieces 17, 17' on the bridge C.
It will be seen that, though that part of the wire W emerging from the nozzle 9 may be somewhat bent at the start of a wiring operation, the guide plate 12 and front end clamping plate 11 cooperate to straighten the wire for thereby ensuring steady restraint of the wire on the wiring block A-1.
Suppose that the wire W stretched from the wiring block A-1 has arrived at a second wiring block A-2 shown in FIG. 7c which is opposed to the wiring block A-1 and defines a point where said wire laying operation is to terminate. The nozzle 9 moves onto the second wiring block A-2 through between adjacent nozzle guide pins 1 and contacts with the upper end of a corresponding nozzle guide groove 5 while bending itself between the pins 1 and groove 5. In the condition shown in FIG. 7c, the wire W outside the nozzle 9 has been stretched in a rectilinear way from the wiring block A-1 to the wiring block A-2 by way of the nozzle guide pins 1 and a pin or pins (not shown) studded on the workbench. Therefore, the wire W is positioned on the wiring block A-2 in alignment with the center of the clearance space between opposite clamping pawls 3 and that between opposite pieces 17, 17' on the bridge C.
As the clamping jig 10 is lowered onto the wiring block A-2, the rear end clamping plate 15 presses the wire W this time in place of the front end clamping plate 11 until the wire W becomes retained between the clamping pawls 3. At the same time, the cutter 14 on the jig 10 cuts the wire W on the surface 4 leaving another predetermined length l of wire protruded from the nozzle 9.
Thereupon, the motor M (see FIG. 3) is energized to rotate the clamping jig 10 by a regulated angular distance which will locate the jig 10 right behind the wiring jig 8. This sets up the same situation as that in FIG. 7a for performing another wiring operation. In this manner, the wiring head B with the wiring jig 8 and clamping jig 10 is moved between desired wiring blocks to lay and cut wires in a continuous fashion while causing opposite ends of each wire W to be located between adjacent upright pieces 17, 17' on a bridge C and retained by adjacent pawls 3.
FIG. 8 illustrates an exemplary design of a wire harness E which has wires W laid between wiring blocks A-1 to A-7 which are placed on the workbench D. Pins 18 are studded on the workbench to hold the wires W in desired orientations. The wires W are suitably bundled up by tapes 19 as indicated.
The workbench D carrying the wire harness E is transferred along guide rails R to the next working station whereat the wires W and bridges C are rigidly connected together by fusing with use of a fusing jig (not shown). Then the wire harness E is removed from all of the wiring blocks A-1 to A-7. Finally, the insulative covering having the predetermined length l of each wire protruding from a bridge C is peeled off and the peeled wire is fitted with a metal terminal member by a device not illustrated in the drawings.
As has been described, the upright pieces 17, 17' on bridge C are connected rigidly with wire ends by fusing them after a wire laying step. In view of the fact that independent devices are employed to carry out the wire laying step and the subsequent steps of wire end peeling and fitting terminals onto the peeled wire ends, the connection by fusion will eliminate difficulties in the course of transfer of a wire harness from one device to the other or during storage of such a wire harness. Also, a wire harness of this type will make various operations such as peeling easy. It is frequently experienced, however, that the bridges of a wire harness become no longer functional once the terminals on the wire ends are fixed to a connector housing for example.